Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more turbine blades. The turbine blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size and capacity of wind turbines. One such modification has been to increase the length of the rotor blades. However, as is generally known, the deflection of a rotor blade is a function of blade length, along with wind speed, turbine operating states and blade stiffness. Thus, longer rotor blades may be subject to increased deflection forces, particularly when a wind turbine is operating in high-speed wind conditions. These increased deflection forces not only produce fatigue on the rotor blades and other wind turbine components but may also increase the risk of the rotor blades striking the tower.
In order to increase the length of wind turbine rotor blades without adversely affecting the aerodynamic design, a blade insert can be used to increase the span of a rotor blade by an amount generally corresponding to the overall length of the blade insert. In addition, improved methods for installing shear web inserts between the blade insert and an adjacent segment of the rotor blade are being developed for rotor blades that generally include a suction side shell and a pressure side shell and are typically formed using molding processes that are bonded together at bond lines along the leading and trailing edges of the blade. The pressure and suction shells are relatively lightweight and have structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor blade during operation. Thus, to increase the stiffness, buckling resistance and strength of the rotor blade, the body shell is typically reinforced using one or more structural components (e.g. opposing spar caps with a shear web insert configured therebetween) that engage the inner pressure and suction side surfaces of the shell halves.
Such rotor blades, however, are not without issues. One particular issue that has arisen involves the connection of shear clips and shear web inserts and clips in rotor blade extensions. Shear clips have been typically utilized to reinforce the interface between the shear web and spar caps, and are connected to both such components at the shear web—spar cap interface. Because thermoset resins are generally utilized to form such rotor blades, thermoset-based joining techniques such as the application of bonding pastes or hand lay-ups must be utilized to attach the shear clips to the shear web inserts and spar caps. It can thus be difficult and time-consuming to join shear clips and shear web inserts in rotor blades. Further, in many cases, the shear clips and shear web inserts may not completely align with the neighboring shear web and/or spar cap surfaces thereby forming an offset or misalignment. These misalignments occur outside of manufacturing tolerances when connecting the shear web and spar caps. Accordingly, the resulting joints may be sub-optimal.
Accordingly, improved methods for connecting and repairing shear web inserts in wind turbine rotor blades, including modular blades, would be advantageous.